Experimental Analysis of Thermal Environment Effects on Human Strength Performance

Abstract

This paper presents an experimental analysis of the influence of thermal environmental conditions on human strength performance. Controlled laboratory experiments were conducted under different ambient temperature and relative humidity levels to assess their impact on maximum force generation, endurance time, and fatigue behavior. Human participants performed standardized strength tasks, and performance metrics along with subjective fatigue responses were recorded and analyzed. The experimental results indicate that thermal stress has a significant effect on strength performance, with higher thermal loads causing a noticeable reduction in force output and faster onset of fatigue, whereas thermally neutral conditions support improved strength sustainability. The outcomes of this study provide important insights for ergonomics design, occupational safety, and human–machine interaction, particularly for tasks performed in thermally demanding environments.

Introduction

This study investigates how thermal environmental conditions (temperature and humidity) affect human strength performance, an important factor in occupational, industrial, and outdoor work. Thermal stress influences physiological processes such as thermoregulation, cardiovascular function, muscle metabolism, and neuromuscular coordination, which directly impact strength, endurance, and fatigue. High temperatures and humidity increase thermal strain, accelerate fatigue, reduce force output, and impair motor control, while cold environments decrease muscle elasticity and nerve conduction, leading to reduced strength and increased stiffness.

The literature review highlights extensive research on thermal comfort, thermal stress, and human performance. Previous studies have shown that heat stress reduces physical capacity, endurance, and labor productivity, while thermal comfort strongly affects human behavior and activity levels. However, most existing research focuses on endurance and cardiovascular responses, with limited attention given to short-duration strength tasks relevant to industrial and manual labor settings. This gap motivates the need for controlled experimental studies examining strength performance under different thermal conditions.

To address this issue, the study proposes a controlled laboratory experiment involving 12 healthy adult participants. Subjects performed standardized isometric handgrip strength tests under three thermal environments: neutral (24°C, 50% RH), moderate heat (32°C, 60% RH), and high heat stress (38°C, 70% RH). Performance was assessed using maximum voluntary contraction (MVC) and endurance tests at 50% MVC, while subjective measures such as perceived exertion and thermal discomfort were also recorded. Environmental conditions were carefully controlled, and statistical analysis was conducted using repeated-measures ANOVA.

The results demonstrate a clear decline in strength performance with increasing thermal stress. Average maximum force output decreased from 410 N under neutral conditions to 372 N in moderate heat and 335 N under high heat stress. Similarly, endurance time decreased from 68 seconds in neutral conditions to 54 seconds in moderate heat and 41 seconds in high heat stress, while fatigue occurred more rapidly. These reductions are attributed to increased cardiovascular strain, impaired heat dissipation, elevated body temperature, and greater perceived exertion.

Conclusion

This study experimentally investigated the effects of thermal environmental conditions on human strength performance and demonstrated that increasing temperature and humidity significantly reduce maximum force output, endurance time, and overall task sustainability while increasing perceived exertion and fatigue. The results confirm that thermally neutral environments support optimal strength performance, whereas moderate and high thermal stress conditions accelerate physiological strain and performance degradation. These findings provide valuable insights for ergonomics design, occupational safety, and human-centered system development, particularly in thermally demanding workplaces. As a future scope, this work can be extended by incorporating a larger and more diverse subject population, additional physiological parameters such as heart rate and core body temperature, and dynamic or task-specific strength activities. Furthermore, the integration of predictive models using machine learning and real-time wearable sensing systems can enable adaptive thermal management and personalized work–rest strategies to enhance human performance and safety under varying thermal environments.

References

[1] Bruse, M. (2009). Analysing human outdoor thermal comfort and open space usage with the Multi-Agent System BOT world. In Seventh International Conference on Urban Climate (ICUC-7). ICUC, Yokohama. [2] Dunne, J. P., Stouffer, R. J., & John, J. G. (2013). Reductions in labour capacity from heat stress under climate warming. Nature Climate Change, 3, 563-566. [3] Bruse, M., & Fleer, H. (1998). Simulating surface–plant–air interactions inside urban environments with a three-dimensional numerical model. Environmental Modelling & Software, 13(3-4), 373-384. [4] Burton, A. C., & Edholm, O. G. (1955). Man in a cold environment. Physiological and pathological effects of exposure to low temperatures. Edward Arnold, London. [5] Farajzadeh, H., Saligheh, M., Alijani, B., & Matzarakis, A. (2015). Comparison of selected thermal indices in the northwest of Iran. Natural Environment Change, 1(1), 1-20. [6] Cadarette, B. S., Montain, S. J., Kolka, M. A., Stroschein, L., Matthew, W., & Sawka, M. N. (1999). Cross validation of USARIEM heat strain prediction models. Aviation, Space, and Environmental Medicine, 70, 996-1006. [7] Carlucci, S., & Pagliano, L. (2012). A review of indices for the long-term evaluation of the general thermal comfort conditions in buildings. Energy and Buildings, 53, 194-205. [8] Chen, L., & Ng, E. (2012). Outdoor thermal comfort and outdoor activities: A review of research in the past decade. Cities, 29(2), 118-125. [9] Chen, Q. (2009). Ventilation performance prediction for buildings: A method overview and recent applications. Building and Environment, 44(4), 848-858. [10] Chen, Y. C., Lin, T. P., & Matzarakis, A. (2014). Comparison of mean radiant temperature from field experiment and modelling: a case study in Freiburg, Germany. Theoretical and Applied Climatology, 118(3), 535-551. [11] Cheng, V., Ng, E., Chan, C., & Givoni, B. (2012). Outdoor thermal comfort study in a sub-tropical climate: a longitudinal study based in Hong Kong. International Journal of Biometeorology, 56(1), 43-56. [12] CIBSE. (2006). Guide A. Environmental Design. Chartered Institution of Building Services Engineers. London. [13] Cutter, S. L., & Finch, C. (2008). Temporal and spatial changes in social vulnerability to natural hazards. Proceedings of the National Academy of Sciences, 105(7), 2301-2306. [14] Cutter, S. L., Boruff, B. J., & Shirley, W. L. (2003). Social vulnerability to environmental hazards. Social Science Quarterly, 84(2), 242-261. [15] Cutter, S. L., Emrich, C. T., Webb, J. J., & Morath, D. (2009). Social vulnerability to climate variability hazards: A review of the literature. Final Report to Oxfam America, 1-44. [16] Cutter, S. L., Mitchell, J. T., & Scott, M. S. (2000). Revealing the vulnerability of people and places: a case study of Georgetown County, South Carolina. Annals of the Association of American Geographers, 90(4), 713-737. [17] Dash, S. K., Jenamani, R. K., Kalsi, S. R., & Panda, S. K. (2007). Some evidence of climate change in twentieth-century India. Climatic Change, 85(3-4), 299-321. [18] de Dear, R., Brager, G. S., & Cooper, D. (1997). Developing an adaptive model of thermal comfort and preference-Final Report (ASHRAE RP 884). ASHRAE, Atlanta. [19] de Freitas, C. R. (1985). Assessment of human bioclimate based on thermal response. International Journal of Biometeorology, 29(2), 97-119. [20] de Freitas, C. R., & Grigorieva, E. A. (2009). The Acclimatization Thermal Strain Index (ATSI): a preliminary study of the methodology applied to climatic conditions of the Russian Far East. International Journal of Biometeorology, 53(4), 307-315. [21] de Freitas, C. R., & Grigorieva, E. A. (2015). A comprehensive catalogue and classification of human thermal climate indices. International Journal of Biometeorology, 59(1), 109-120. [22] De Freitas, C. R., & Ryken, M. G. (1989). Climate and physiological heat strain during exercise. International Journal of Biometeorology, 33(3), 157-164. [23] De Freitas, C. R., & Symon, L. V. (1987). A bioclimatic index of human survival times in the Antarctic. Polar Record, 23(147), 651-659. [24] de Paula Xavier, A. A., & Lamberts, R. (2000). Indices of thermal comfort developed from field survey in Brazil. ASHRAE Transactions, 106(1), 45-58. [25] Dovie, D. B., Dzodzomenyo, M., & Ogunseitan, O. A. (2017). Sensitivity of health sector indicators\' response to climate change in Ghana. Science of the Total Environment, 574, 837-846.

Copyright

Copyright © 2026 Vineet Chaudhary, Ashutosh Singh, Rahul Bhatnagar, Sharad Kumar, Sushil Kumar Jha. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.